matseng wrote:It seems like most stepper boards are using integrated solutions.
Yep, they're inexpensive require little board space (quick also adds to the inexpensiveness) and are easy to design in.
Is it very very hard to make the h-bridges with discrete fets, drivers and a microcontroller if you also want microstepping? Just wondering - I've never been fiddling with motor drivers....
Usually, you'll use a translator IC to take care of the chopping and microstepping and then do the discrete FET's or maybe an H-bridge IC in a large package. It is more involved (and costs more). I think most hobbyist applications find that they can get away with using the integrated solutions, so they do. I'd like to get into some higher power discrete solutions in the future.
Sleepwalker3 wrote:OK. Please don't take my suggestions or questions as negative, just I see a lot of people making 'simple to make' mistakes. If I'm telling you how to suck eggs, then let me know.
Not at all. I make far more mistakes than I'd like (a lot of times when I (should) know better). I really do appreciate all the input!
If I come off as being defensive - it's certainly not intentional :(
Sleepwalker3 wrote:you can usually (depending on the application) get away quite happily with 5 or 6 mA per LED and be more than bright enough for most indicator applications...I'd suggest trying your leds out with a 1K and see if they're bright enough, I think you'll find they are.
Yeah, I'll definitely be trying out a lower current.
Sleepwalker3 wrote:I reckon you are really tempting fate trying to pump 24V into a little baby regulator like that, as you noted, the dissipation is going to be pretty mean.
While driving the LED's in their existing configuration, this correct. The worst-case won't be so bad if the LED current is reduced down to 5-6mA ea (even then I'm still looking at dissipating around 2 watts worst case (.006mA * 12 LED's * 30 volt drop). On the positive side, the regulator specified ( IFX27001) has built in thermal protection, so if things do overheat, it shouldn't cause any permanent damage. Admittedly, I wouldn't think about using an LDO in this capacity for something I was doing in my professional life. . .
I know hobbyists try to save every cent, but would $10 be too much if you had a readily available source of switch reg that would fit in a TO220 footprint? If that sounds OK, I'll point you in the right direction.
I think in this case the $10 probably is too much, although I'm always curious to hear what other people like ( I had a bad experience with a "Simple Switcher" once :( - I think it was due to a poor layout).
Sleepwalker3 wrote:How are you working the logic on the E-Stop button, i.e. It looks like you're expecting to bridge the connection when the button is pressed in (i.e. when there is an emergency), thereby pulling E-STOP_IN high, pulls the output of the buffer high, sends a high to the PC, sends a high via D2 which eventually ends up pulling the /Enable Line on the Driver chip high, thereby Disabling it - Correct?
Spot on. This arrangement also allows the PC to supply an ESTOP. Certainly not as robust as going directly into a relay that cuts power to the whole thing. Admittedly, this is a bit indirect and doesn't even allow for a single point of failure (the buffer), but it seemed like a step in the right direction from the usual purely software-implemented ESTOP's. Suggestions?
Sleepwalker3 wrote: Could you route the section of the board under the chip (have your fab do it later obviously!) and fit up a block of aluminium (or Aluminum if you're a yank) into the cut-out, obviously a good thermal interface medium between the two, and transfer the heat down to the chassis, where again you use a good thermal interface medium?
Aluminum for the yank ;-) and you'll also find that I tend to speak in terms of mils and inches ( I fully realize I'm in the minority here, but until I can actually visualize what a mm is I'll have to live with my curse. . .) I was really hoping that this board could be used with or without external heat sinking (not up to the max ratings without external heat sinking of course). I like the idea of an Al block under a routed portion of the board, but this would necessitate the need for an external enclosure (which isn't a desirable requirement to impose). I've had good luck with a 4 layer board with the same chip and a similar layout tied to a chassis sheet metal. I need to do a bit of research and figure out if it's reasonable to expect similar performance from 2oz/inch copper and a thinner FR4 substrate (probably not) - more along the lines of 0.8mm.